Off-highway implements, such as front-end loaders and the like are typically provided with a loader mechanism at one end thereof. A conventional loader mechanism includes a working tool such as a bucket or the like pivotally connected to a frame of the implement by longitudinally extending loader arms. A series of hydraulic actuators, usually in the form of double-acting hydraulic cylinders, are connected to a hydraulic system of the implement for effecting various loader functions. Hydraulic actuators are used to elevate the bucket or tool by raising and lowering the loader arms. Hydraulic actuators are likewise used to control the roll or pivotal movement of the bucket relative to the loader arms. Many loader mechanisms further incorporate a device such as a clam shell bucket which utilize other hydraulic actuators for controlling articulated movements of the clam shell bucket to effect a "grab" function.
Control over the various loader functions or work operations is conventionally achieved through manipulation of various control levers. Each control lever is typically connected to a controller which serves to mount the control lever to the implement frame and includes a linkage mechanism for transferring and translating movement of the control lever into positional movements for a control valve. The control valve, in turn, regulates hydraulic fluid flow between a pressurized hydraulic source on the implement and each of the actuators.
In addition to controls for the loader mechanism, a cab region of an off-highway implement is replete with other mechanisms and devices for regulating braking, steering, and speed of the implement. Typically, such devices include linkage mechanisms including a series of interconnected links for transferring movement in response to an operator's controls. As will be appreciated, such linkage mechanisms are independently operable and thus must be sufficiently spaced from each other to accommodate the various movements of the links without causing interferences therebetween. Accordingly, space availability beneath and about the cab area of an off-highway implement is severely limited. Adding separate controllers to allow for manipulation of each control lever further complicates the control mechanism of the off-highway implement and further complicates space availability in an area already replete with moving mechanisms. The addition of separate controllers for each control lever also adds significantly to manufacturing costs by requiring substantially duplicative parts for the different control levers.
During operation of the implement, the loader mechanism can perform a single function but usually at least two loader functions are affected simultaneously. That is, while the loader arms are being elevationally positioned, the pivotal position or roll of the bucket may likewise be adjusted. When equipped with a clam shell bucket, all three loader functions may be effected simultaneously to economize on operational time for the implement. As will be appreciated, controlling the implement's direction and speed simultaneously with raising, lowering, tilting, and articulating the bucket of the loader mechanism through movement of a multiplicity of control levers can become a cumbersome task for anyone to perform successfully.
Thus, there is a need and a desire for a three function control mechanism including a single controller for mounting a control handle to the frame of the implement such that various loader functions can readily be effected either independently of one another or in unison with one another or, in any combination desired by the operator with a minimum number of parts so as to reduce the complexity of the mechanisms for accomplishing these results.